1. Technical Field of the Invention
The present invention relates to a drawing device, and in particular, a drawing device providing stable ink droplet ejection, an electro-optical unit and an electronic apparatus manufactured by using the drawing device.
2. Description of the Related Art
A liquid drop emitter for ejecting droplets of writing liquid, such as ink, to a color filter used for a liquid crystal display device or the like includes, for example, an inkjet head for ejecting ink. Such an inkjet head has an ink nozzle for ejecting ink. Ink ejected from the ink nozzle is applied to the color filter. In particular, the inkjet head has a piezo-electric element, which deforms in accordance with an applied voltage to eject the ink from the ink nozzle. Thus, an inkjet head that can easily control the ejection of the ink is achieved. A method ejecting ink in this manner is referred to as an inkjet method.
With reference to FIG. 12, an inkjet head 12 for the inkjet method has a plurality of ink nozzles 37, for example, 180 nozzles per line, on its bottom surface. Liquid ink is intermittently ejected from the ink nozzles and the ink is disadvantageously deposited on the tops of the ink nozzles or on the inner surfaces of the nozzles due to an inevitable increase in viscosity of the ink after long-term use.
Using the ink nozzles with the deposited ink results in misdirected ink ejected from the ink nozzles or clogged ink nozzles due to the deposited ink, which, in turn, results in faulty ejection of the ink nozzles.
Therefore, with reference to FIG. 13 illustrating a known technology, a substrate 1, to which the ink is ejected, is mounted on a stage 16. The stage 16 has ink trays 9 for receiving the ink from the inkjet head 12 in a standby mode. In particular, the ink trays 9 are disposed in an area where the inkjet head moves away from the ink-application area of the substrate.
The inkjet head 12 moves to the locations of the ink trays 9 and ejects ink thereto unless the inkjet head 12 ejects ink onto the substrate, such as a color filter. This action is known as “flushing”. Such flushing of the ink prevents the ink nozzles from becoming clogged with the ink sticking to the inner surface of the nozzles due to ink thickening.
Unfortunately, in the known inkjet method described above, the flushing operation causes the following problems:
the flushing wastes ink;
the flushing is time-consuming and thereby increases the total drawing time; and
the flushing requires various means and thereby increases the cost of the drawing device.
Accordingly, an object of the present invention is to provide a drawing device that ejects droplets stably without the flushing required in the known technology, and to provide an electro-optical unit and an electronic apparatus manufactured by using the drawing device.